Bill Preston, a graduate of Penn State, joined Sun Oil – which later would become Sunoco – in the mid-‘50s. In 1966 he was assigned by Sunoco to support Penske Racing, and in that role traveled with the Penske team all over the U.S. and Canada while it competed in the USRRC, Trans-Am and Can-Am series. Retiring in 1992, Bill and his wife Joan have enjoyed Prescott, Arizona since moving there in 1995. Bill brings to the following a well-informed perspective, almost 50 years since the oil industry ‘got the lead out’.
Tetraethyl lead, abbreviated as TEL, was discovered to be useful as an anti-knock compound by Thomas A. Midgley, who worked for Charles F. (“Boss”) Kettering at Delco. Midgley began his work in 1916 when he saw that an engine’s fuel economy could be improved by increasing its compression ratio, but that was not possible because of poor octane quality. In 1918 geologists predicted that only 20-30 years of crude oil were left in the United States. Midgley’s work intensified, trying to improve aviation gasoline at the Army Air Corps field in Dayton during WWI. On December 9, 1921 he found an effective, economical additive with the chemical formula (CH3CH2)4Pb. TEL serves as a gasoline-soluble carrier for the lead, and the lead produces a smooth ignition with a hot flame front which produces carbon dioxide, water and lead. However, the leftover lead would accumulate in the engine and ruin it. To remove the lead, “lead scavengers”, 1,2 dibromoethane and 1,2 dichloroethane are added to the TEL to expel the lead from the engine as lead bromide and lead chloride.
Delco was absorbed into General Motors and Kettering became GM’s vice president in charge of General Motors Research. He proposed the name “ethyl gasoline,” and General Motors and Standard Oil of New Jersey went together to form Ethyl Corporation for the manufacture of TEL. DuPont owned 14% of GM at the time, so they were invited to manufacture TEL as well.
By regulation, any leaded fuel is – and has been since the 1920s – dyed. Regular grade was dyed orange and premium usually red. But the rule only said that it had to be dyed. ‘White gasoline’ was sold, having no lead and – subsequently – no dye.
Sunoco chose blue to differentiate its product from all others, as it was – justifiably – proud of its product. When I joined Sun there were regional engineers. If you called the company and said you were having a problem with our gasoline (frequent problems back in the day included fuel pump failure, vapor lock and no carburetor heat) one of them was sent to your home. When he opened the hood, if Sunoco was being used the carburetor would be tinted blue. If it wasn’t, the Sunoco rep might help you…or he might just close the hood.
So, Sunoco 260 (1957-1973) was dyed blue and had nearly the legal upper limit of tetraethyl lead (TEL) of 3.0 ml/gal, which produced the 103.6 Research octane we bragged about: “the highest-octane commercial gasoline in the world”.
Mixing TEL in gasoline began to end in 1974 for two reasons: (1) research in the 1960s and ‘70s showed that children living near Interstates or major highways had lower scores in standardized school tests than did kids living on farms or in the country, and further research showed a higher presence of lead in their bodies; and (2) TEL would contaminate the catalytic mufflers which were introduced nationwide in 1974.
You may remember that Amoco premium was always unleaded. That was their ‘different or unique’ fuel. It turned out that, unknown to the automotive and petroleum industries, the lead in gasoline was serving as a lubricant for engine valve seats. Without lead, the valves would recess into the cylinder head. The result was that the engine gradually wouldn’t idle, and the idle speed had to be set up higher. Amoco customers never had this effect because every so often they couldn’t find an Amoco station and had to use leaded fuel. That was enough to coat the seats, so they never had a problem.
Sun participated in a test of our prototype unleaded fuel, conducted by Southwest Research Institute in Texas. We supplied a tank car of unleaded fuel. They contracted with the Texas Highway Patrol to run it in their vehicles. In those days (early 1970s) they used Plymouth Furys with 383 cubic-inch V-8s, four-barrel carburetors and 335 bhp. They could do an honest 100 mph. The trooper would sit on an Interstate bypass with radar, idling to keep the A/C and police radio and radar working. I don’t remember the speed limit, but soon someone would come by over the limit at, say, 80 mph (this is Texas!) and the trooper would slide down off the on-ramp and floor his Plymouth.
This becomes a calculus problem: How soon will a car starting from a standstill and reaching 100 mph catch up with a speeding car cruising at 80? I think the answer is around five minutes. After issuing the ticket, the trooper would go back to his spot on the bypass or on-ramp and idle until the next violator came along. Soon his interceptor wouldn’t idle to run the alternator. The trooper garage would set the idle up, but it would get lumpy and soon the car wouldn’t idle, period!
General Motors solved the problem for the car industry by introducing induction-hardened cylinder head ports. On the production line for cast iron cylinder heads they use a magnetic induction coil that heats and hardens the valve seats without touching them. This eliminated the necessity of machining the ports to accept valve seats. The whole industry adopted GM’s solution and your car has this today.
Aviation fuel for small piston-engine aircraft (like Cessna) still use leaded fuel today. They received a pass from the federal government because the FAA wasn’t willing to take the chance on doing a valve job on thousands of small airplanes, and they didn’t put enough lead in the air to matter, and (finally) little kids weren’t around airports. Forty-five years later private airports have 100LL (low lead) fuel! Also, Sunoco still makes about 15 varieties of racing fuel, about half of them dyed and containing TEL. They are not allowed to be used on the highway and are very expensive; unless you have some kind of special performance car you couldn’t afford to waste them on the highway. They are legal for drag strips and some oval circuits. Associations like NASCAR, SCCA, CART, etc. require unleaded fuel to be used, and almost all is provided by Sunoco these days.